Knee dislocation

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Knee dislocation
PosteriorKneeDIsclocation.jpg
Plain lateral X-ray of the left knee showing a posterior knee dislocation [1]
Specialty Orthopedic surgery  OOjs UI icon edit-ltr-progressive.svg
Symptoms Knee pain, knee deformity [2]
Complications Injury to the artery behind the knee, compartment syndrome [3] [4]
TypesAnterior, posterior, lateral, medial, rotatory [4]
Causes Trauma [3]
Diagnostic method Based on history of the injury and physical examination, supported by medical imaging [5] [2]
Differential diagnosis Femur fracture, tibial fracture, patellar dislocation, ACL tear [6]
Treatment Reduction, splinting, surgery [4]
Prognosis 10% risk of amputation [4]
Frequency1 per 100,000 per year [3]

A knee dislocation is an injury in which there is disruption of the knee joint between the tibia and the femur. [3] [4] Symptoms include pain and instability of the knee. [2] Complications may include injury to an artery, most commonly the popliteal artery behind the knee, or compartment syndrome. [3] [4] [7]

Contents

About half of cases are the result of major trauma and about half as a result of minor trauma. [3] About 50% of the time, the joint spontaneously reduces before arrival at hospital. [3] Typically there is a tear of the anterior cruciate ligament, posterior cruciate ligament, and either the medial collateral ligament or lateral collateral ligament. [3] If the ankle–brachial pressure index is less than 0.9, CT angiography is recommended to detect blood vessel injury. [3] Otherwise repeated physical exams may be sufficient. [2] More recently, the FAST-D protocol, assessing the posterior tibial and dorsalis pedis arteries for a ‘tri-phasic wave pattern’ with ultrasound, has been shown to be reliable in ruling out significant arterial injury. [8]

If the joint remains dislocated, reduction and splinting is indicated; [4] this is typically carried out under procedural sedation. [2] If signs of arterial injury are present, immediate surgery is generally recommended. [3] Multiple surgeries may be required. [4] In just over 10% of cases, an amputation of part of the leg is required. [4]

Knee dislocations are rare, occurring in about 1 per 100,000 people per year. [3] Males are more often affected than females. [2] Younger adults are most often affected. [2] Descriptions of this injury date back to at least 20 BC by Meges of Sidon. [9]

Signs and symptoms

CT angiogram 3D reconstruction, posterior view showing a normal artery on the left, and occlusion to right popliteal artery as a result of a knee dislocation CTAngioOcclusionRtPop.jpg
CT angiogram 3D reconstruction, posterior view showing a normal artery on the left, and occlusion to right popliteal artery as a result of a knee dislocation

Symptoms include knee pain. [2] The joint may also have lost its normal shape and contour. [2] A joint effusion may, or may not, be present. [2]

Complications

Complications may include injury to the artery behind the knee (popliteal artery) in about 20% of cases or compartment syndrome. [3] [4] Damage to the common peroneal nerve or tibial nerve may also occur. [2] Nerve problems, if they occur, often persist to a variable degree. [11]

Cause

About half are the result of major trauma, the other half as a result of minor trauma. [3] Major trauma may include mechanisms such as falls from a significant height, motor vehicle collisions, or a pedestrian being hit by a motor vehicle. [2] Cases due to major trauma often have other injuries. [5]

Minor trauma may include tripping while walking or while playing sports. [2] Risk factors include obesity. [2]

The condition may also occur in a number of genetic disorders such as Ellis–van Creveld syndrome, Larsen syndrome, and Ehlers–Danlos syndrome. [12]

Diagnosis

A Segond fracture seen on X-ray SegondFracture.JPG
A Segond fracture seen on X-ray

As the injury may have self-reduced before arrival at hospital, the diagnosis may not be readily apparent. [2] Diagnosis may be suspected based on the history of the injury and physical examination [5] which may include anterior drawer test, valgus stress test, varus stress test, and posterior sag test. [5] An accurate physical exam can be difficult due to pain. [5]

Plain X-rays, CT scan, ultrasonography, or MRI may help with the diagnosis. [2] [11] Findings on X-ray that may be useful among those who have already reduced include a variable joint space, subluxation of the joint, or a Segond fracture. [5]

If the ankle–brachial pressure index (ABI) is less than 0.9, CT angiography is recommended. [3] Standard angiography may also be used. [2] If the ABI is greater than 0.9 repeated physical exams over the next 24 hours to verify good blood flow may be sufficient. [2] [11] The ABI is calculated by taking the systolic blood pressure at the ankle and dividing it by the systolic blood pressure in the arm. [2] More recently, the FAST-D protocol, using ultrasound to assess the posterior tibial and dorsalis pedis arteries for a ‘tri-phasic wave pattern’, has been shown to be reliable in ruling out significant arterial injury. [8]

Classification

A lateral dislocation of the knee Lateral-knee-dislocation-1.jpg
A lateral dislocation of the knee

They may be divided into five types: anterior, posterior, lateral, medial, and rotatory. [4] This classification is based on the movement of the tibia with respect to the femur. [11] Anterior dislocations, followed by posterior, are the most common. [2] They may also be classified on the basis of which ligaments are injured. [2]

Treatment

Initial management is often based on Advanced Trauma Life Support. [5] If the joint remains dislocated reduction and splinting is indicated. [4] Reduction can often be done with simple traction after the person has received procedural sedation. [11] If the joint cannot be reduced in the emergency department, then emergency surgery is recommended. [2]

In those with signs of arterial injury, immediate surgery is generally carried out. [3] If the joint does not stay reduced external fixation may be needed. [2] If the nerves and artery are intact the ligaments may be repaired after a few days. [11] Multiple surgeries may be required. [4] In just over 10% of cases an amputation of part of the leg is required. [4]

Epidemiology

Knee dislocations are rare: they represent about 1 in 5,000 orthopedic injuries, [5] and about 1 knee dislocation occurs annually per 100,000 people. [3] Males are more often affected than females, and young adults the most often. [2]

References

  1. ↑ Duprey K, Lin M (February 2010). "Posterior knee dislocation". The Western Journal of Emergency Medicine. 11 (1): 103–4. PMC   2850837 . PMID   20411095.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Boyce RH, Singh K, Obremskey WT (December 2015). "Acute Management of Traumatic Knee Dislocations for the Generalist". The Journal of the American Academy of Orthopaedic Surgeons. 23 (12): 761–8. doi:10.5435/JAAOS-D-14-00349. PMID   26493970. S2CID   10713473.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Maslaris A, Brinkmann O, Bungartz M, Krettek C, Jagodzinski M, Liodakis E (August 2018). "Management of knee dislocation prior to ligament reconstruction: What is the current evidence? Update of a universal treatment algorithm". European Journal of Orthopaedic Surgery & Traumatology. 28 (6): 1001–1015. doi:10.1007/s00590-018-2148-4. PMID   29470650. S2CID   3482099.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Bryant B, Musahl V, Harner CD (2011). "59. The Dislocated Knee". In W. Norman Scott (ed.). Insall & Scott Surgery of the Knee E-Book (5th ed.). Elsevier Churchill Livingstone. p. 565. ISBN   978-1-4377-1503-3.
  5. 1 2 3 4 5 6 7 8 Lachman JR, Rehman S, Pipitone PS (October 2015). "Traumatic Knee Dislocations: Evaluation, Management, and Surgical Treatment". The Orthopedic Clinics of North America. 46 (4): 479–93. doi:10.1016/j.ocl.2015.06.004. PMID   26410637.
  6. ↑ Eiff MP, Hatch RL (2011). Fracture Management for Primary Care E-Book. Elsevier Health Sciences. p. ix. ISBN   978-1455725021.
  7. ↑ Medina O, Arom GA, Yeranosian MG, Petrigliano FA, McAllister DR (September 2014). "Vascular and nerve injury after knee dislocation: a systematic review". Clinical Orthopaedics and Related Research. 472 (9): 2621–9. doi:10.1007/s11999-014-3511-3. PMC   4117866 . PMID   24554457.
  8. 1 2 Montorfano, Miguel Angel; Montorfano, Lisandro Miguel; Perez Quirante, Federico; Rodríguez, Federico; Vera, Leonardo; Neri, Luca (December 2017). "The FAST D protocol: a simple method to rule out traumatic vascular injuries of the lower extremities". Critical Ultrasound Journal. 9 (1): 8. doi: 10.1186/s13089-017-0063-2 . PMC   5360748 . PMID   28324353.
  9. ↑ Elliott JS (1914). Outlines of Greek and Roman Medicine. Creatikron Company. p. 76. ISBN   9781449985219.{{cite book}}: ISBN / Date incompatibility (help)
  10. ↑ Godfrey AD, Hindi F, Ettles C, Pemberton M, Grewal P (2017). "Acute Thrombotic Occlusion of the Popliteal Artery following Knee Dislocation: A Case Report of Management, Local Unit Practice, and a Review of the Literature". Case Reports in Surgery. 2017: 5346457. doi: 10.1155/2017/5346457 . PMC   5299179 . PMID   28246569.
  11. 1 2 3 4 5 6 Pallin DJ, Hockberger R, Gausche-Hill M (2018). "50. Knee and lower leg". In Walls RM (ed.). Rosen's Emergency Medicine – Concepts and Clinical Practice E-Book (9th ed.). Philadelphia: Elsevier Health Sciences. p. 618. ISBN   978-0-323-35479-0.
  12. ↑ Graham JM, Sanchez-Lara PA (2016). "12. Knee dislocation (Genu Recurvatum)". Smith's Recognizable Patterns of Human Deformation E-Book (4th ed.). Philadelphia: Elsevier. p. 81. ISBN   978-0-323-29494-2.
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